Many Unix-like systems, in particular Linux, simply ignore the
setuid and setgid bits on scripts to avoid the race condition
described earlier.
Since support for setuid scripts varies on Unix-like systems,
they’re best avoided in new applications where possible.
As a special case, Perl includes a special setup to support setuid Perl
scripts, so using setuid and setgid is acceptable in Perl if you
truly need this kind of functionality.
If you need to support this kind of functionality in your own
interpreter, examine how Perl does this.
Otherwise, a simple approach is to “wrap” the script with a small
setuid/setgid executable that creates a safe environment
(e.g., clears and sets environment variables) and then
calls the script (using the script’s full path).
Make sure that the script cannot be changed by an attacker!
Shell scripting languages have additional problems, and really should
not be setuid/setgid; see Section 10.4
for more information about this.